updated HOWTO-ZENITH.md

## 1. Preparing enviroment for Zenith

Our ensembling shell script requires a python3.6 virtual enviroment named zenithenv, placed in `/swp-metaphors/zenith/`. 

	- If you are interested in running an ensemble model execute these commands in `/swp-metaphors/zenith/`

* If you are interested in running an ensemble model execute these commands in `/swp-metaphors/zenith/`

      ```

      virtualenv -p python3.6 --system-site-packages zenithenv

      source zenithenv/bin/activate

      pip install -r requirements.txt

      deactivate

      ```

	- If you only want to train single models, you can directly install the required librarys by executing

* If you only want to train single models, you can directly install the required librarys by executing

      `pip install -r requirements.txt`.